1. Statement of the Technical Field
The inventive arrangements relate to radio communications and more particularly to improvements in symbol sampling in communications environments where a significant amount of delay spread exists.
2. Description of the Related Art
Simulcast systems create delay spread at receive sites that is proportional to site spacing. The delay spread is known to degrade the bit-error-rate (BER) of receive radios in site overlap areas. Coverage area of a simulcast system can be improved by reducing the adverse effects that delay spread has upon BER. When the coverage area is improved in this way, the number of simulcast transmitter sites can be reduced, thereby lowering overall infrastructure costs.
Symbol synchronization is used to estimate the optimal time for sampling each symbol in a received signal. Improved symbol synchronization is a key factor for purposes of reducing BER. Conventional synchronization methods involve correlating a burst of a limited number of received symbols contained in a “synchronization field” with a known set of reference symbols. The symbols contained in the synchronization field do not represent user data and therefore comprise overhead in the communication system. Accordingly, the number of symbols contained in the synchronization field and the frequency of such fields is intentionally limited.
The foregoing synchronization approach maximizes the available bandwidth for throughput of user data. Still, due to the limited number of synchronization symbols, conventional synchronization methods take a relatively long time to converge to the optimal synchronization time when operating in a high delay spread environment. This slow synchronization process can severely degrade the time required to establish initial synchronization and call start.